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94 sierra thermac


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dr.donut
User

Dec 19, 2015, 12:34 PM

Post #1 of 28 (926 views)
94 sierra thermac Sign In

I've been looking for the thermatic actuator for a 94 gmc sierra 1500 pick up truck with a 5.0, The part in the air cleaner that diverts air flow from normal to the exhaust manifold for faster warm up. You can google the part # 2509 9172 and a few sites come up but it turns out the part is discontinued on all. Is there any other places I can try or maybe modify a similar part for faster warm up? Thanks


Hammer Time
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Dec 19, 2015, 12:52 PM

Post #2 of 28 (923 views)
Re: 94 sierra thermac Sign In

No. It's not for faster warm up. It's there to supply heated air into the intake for better fuel consumption during cold starts. It won't do anything to make the engine heat up faster.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Dec 19, 2015, 1:21 PM

Post #3 of 28 (918 views)
Re: 94 sierra thermac Sign In

Exactly as HT just said not for warm up rather warm air fast to atomize fuel. Riveted I think on snout of air cleaner. Does save fuel when working and cold operation just a short time as it also thermostatically shuts off for plain air.


What to do? By now probably junk yard a snorkel or whole assy. Make sure the weak and probably rusty heat stove is worth a damn or it really isn't going to do much for you.
Still would be illegal where I am not to have this stuff in place at least by looks at least. If leaking that's a problem. Most folks/techs would seriously consider just let it take in cool air and not leak by plugging hose to it.


Check as it does help if new stuff available or get lucky and find newer used that works. Rock and hard place with the age and the rules of the game,


T



kev2
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Dec 19, 2015, 1:36 PM

Post #4 of 28 (913 views)
Re: 94 sierra thermac Sign In

you could do a patrt # cross fit reference it fit lots of gm's then the salvage (junk) yards, couple of rivets is all.. or google the # 25099172


Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 19, 2015, 1:46 PM

Post #5 of 28 (909 views)
Re: 94 sierra thermac Sign In

High bet you can make this work and find it new somewhere. Junk yards where I am are just squishing anything over 10 years old quickly now with price of metal and space for things that are not going to sell anyway.
Yes - many GMs should fit it's just a diaphragm and a rod to a choke like plate in snorkel.
A warning. If vacuum hose is to be replaced back to plastic vacuum temp sensor try hard to cut and peel it off they get as brittle as can be but those too should be available.
Try NAPA if trouble with this stuff if hard to find,


T



dr.donut
User

Dec 19, 2015, 3:56 PM

Post #6 of 28 (902 views)
Re: 94 sierra thermac Sign In

O.K. At any rate I'd wouldn't mind having it working, this last spring the two back plugs at the fire wall were fouled out, I thought maybe improper warm up had something to do with that. I replaced all plugs. When I bought this truck the therm valve actuator wasn't working and was drawing off the exhaust at all times, I took off the little spring that holds in this position but with cold weather coming I wanted it proper. It's just a small pintel that warms up and pushes the "damper"open for normal draw. All the other hardware is in good shape so I'll keep looking


Hammer Time
Ultimate Carjunky / Moderator
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Dec 19, 2015, 4:01 PM

Post #7 of 28 (900 views)
Re: 94 sierra thermac Sign In

I don't believe you are going to notice any different whatsoever with that part working. It was put there for emissions reasons in the first place.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



dr.donut
User

Dec 19, 2015, 4:27 PM

Post #8 of 28 (897 views)
Re: 94 sierra thermac Sign In

All right, thanks, if it's not important I won't bother, truck runs ,looks good,I think depending on where you get your inspection from in new york they can nit pic over heater tubes and the like, one guy did years ago but I don't go to them anymore.


Hammer Time
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Dec 19, 2015, 5:06 PM

Post #9 of 28 (893 views)
Re: 94 sierra thermac Sign In

I don't think they would even know it came with one if you were able to hide the evidence.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



dr.donut
User

Dec 19, 2015, 5:14 PM

Post #10 of 28 (888 views)
Re: 94 sierra thermac Sign In

Plus being a 94 these "laws" may not even apply, they make a lot of laws and it seems the first thing any one does is find a way around them.


Hammer Time
Ultimate Carjunky / Moderator
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Dec 19, 2015, 8:12 PM

Post #11 of 28 (882 views)
Re: 94 sierra thermac Sign In

If the truck was equipped with it, then it would be required. Best bet is just hide the fact that it's missing. They won't be the wiser.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Dec 20, 2015, 12:39 AM

Post #12 of 28 (876 views)
Re: 94 sierra thermac Sign In

Dr. Donut: Thing doesn't do much at all so as HT suggested is probably what I'd do is plug it off as "HOME" position is open. It is required to work if equipped new just some places don't inspect every last thing or at all.
You do NOT want it to be a vacuum leak is all you should totally care about.
Truck wouldn't start if this thing was so important - it's not just faster to run and burn fuel totally for just a short time.
The fouled back plugs are something you should be paying attention to. This "ThermAC" thing isn't doing that there's another problem.
At the age look all over for vacuum leaks. Hose is cheap by the roll or sold by sections of so many feet requested for which size and type,


T



Discretesignals
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Dec 20, 2015, 7:53 AM

Post #13 of 28 (860 views)
Re: 94 sierra thermac Sign In

You stated your two back plugs were fouled? Fouled with what? Was the engine misfiring on those two back cylinders?

TAC system doesn't have any vacuum hoses on that set up. It uses that wax pellet doodad to regulate the door. It is kind of funny to see a TAC system on a fuel injected vehicle, but I suppose with the injectors being over the intake, it needed some way of regulating the air temperature inside the intake.





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dr.donut
User

Dec 20, 2015, 12:33 PM

Post #14 of 28 (850 views)
Re: 94 sierra thermac Sign In

No vacuum hoses off the air cleaner that I remember,it has a TBI unit, does that count as EFI ? It was idleing a little poor at a stop so I checked the plugs, I think I just happened to pull a back one out and it was black ,sooty the gap was filled, the rest didn't look that great,kinda whooped so I got all new, maybe the back ones are the first to go?Didn't check gaps on old ones just tossed them,I think this truck sat for a while at one time, many coolant flushes were needed to clear the system up, lot of rust color, same with the motor compartment, the guy said it was from the water pump leaking and he replaced it. Must have been leaking for a while to do that. there were Few other dubious repairs also. The heater core line into the intake manifold was cobbed in with a bunch of J B weld or something. And someone put a pan head screw in the rear brake line at the master cyl. because there was a leak in the rear lines. Still a good truck.


Discretesignals
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Dec 20, 2015, 12:58 PM

Post #15 of 28 (847 views)
Re: 94 sierra thermac Sign In

Yep, TBI is a form of EFI. The rear cylinders get a lot of the heat from the engine. I've seen many K and M engines that burned oil and smoked from a stop because the valve guide seals got hard as a rock. Sometimes that can foul a plug. Excess carbon could be from a fuel mixture issue. Were all the plugs dark?

Really kind of hard to see what the computer is doing without a scan tool to look at block learn and the integrator. Those were the early long and short term fuel trim memories that would tell you how the computer was controlling the fuel trim.

Another common issue was the TB base gasket would break and create a vacuum leak under the throttle body. That could cause a rough unstable idle. Sometimes you could actually look down the throttle body and see part of the gasket poking out. The fuel injection system used speed density calculations based off the MAP sensor. A vacuum leak may cause the engine to idle higher and richer.





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(This post was edited by Discretesignals on Dec 20, 2015, 1:02 PM)


dr.donut
User

Dec 20, 2015, 2:00 PM

Post #16 of 28 (837 views)
Re: 94 sierra thermac Sign In

As I remember all the plugs were dark, I've heard to put some oil at the gasket to see if it gets sucked in, No telling what I can find if I check it out.


Tom Greenleaf
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Dec 20, 2015, 3:38 PM

Post #17 of 28 (832 views)
Re: 94 sierra thermac Sign In

Now all plugs were dark - changes the show + might just need new correct ones. Don't put oil on plugs already in! Do use the smallest smear on threads when replacing like a high temp grease - not much,


T



dr.donut
User

Dec 20, 2015, 9:13 PM

Post #18 of 28 (820 views)
Re: 94 sierra thermac Sign In

Plugs being dark is just from memory, like I said they were all whooped so I replaced them. The oil on the gasket I meant on the TB gasket to see if it leaks, to see if the oil gets sucked in, IDK. Thinking back months ago I stopped at a garage and this younger dude said I was running rich, I guess from the smell of the exhaust, the extra fuel or what ever, didn't think much of it.I want to pop the hood to see what vacuum lines are actually on the air cleaner and take a look at things, never know what you'll find.


Tom Greenleaf
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Dec 21, 2015, 1:34 AM

Post #19 of 28 (815 views)
Re: 94 sierra thermac Sign In

No Chev V8 has used gaskets on spark plugs since the 1960s sport. A '94 wants OE Autolite plugs and matters. Taper seated spot will stick hard so don't over tighten and pulling off plug wires get the right tool or you'll wreck new wires in no time.
If running rich it's not this ThermAC thing at all. Vacuum leaks always the first thing to fix or rule out. If really rich for too long you converter is already junk. Code readings for a '94 are not as helpful IMO but worth a try. Even those codes don't or can't really tell you what is wrong but lead to what is the problem. I don't think any OBDI have much memory for a pending problem.
Find out why ASAP and fix it. Lots cheaper and better for truck than waiting,


T



Discretesignals
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Dec 21, 2015, 7:46 PM

Post #20 of 28 (802 views)
Re: 94 sierra thermac Sign In

A spray bottle of water does a better job of finding vacuum leaks than oil. Set the spray bottle so it shoots a stream of water. With the engine running, you'll hear the water get sucked in when it hits a vacuum leak.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


dr.donut
User

Dec 22, 2015, 5:50 AM

Post #21 of 28 (791 views)
Re: 94 sierra thermac Sign In

O.K. Thanks


Hammer Time
Ultimate Carjunky / Moderator
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Dec 22, 2015, 6:10 AM

Post #22 of 28 (790 views)
Re: 94 sierra thermac Sign In

Smoke works even better than that.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Dec 22, 2015, 5:34 PM

Post #23 of 28 (782 views)
Re: 94 sierra thermac Sign In

The Scotty Kilmer way:







Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 22, 2015, 5:50 PM

Post #24 of 28 (777 views)
Re: 94 sierra thermac Sign In

You had to bring that idiot up. He's sucking on exhaust to get a buzz in that picture.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



dr.donut
User

Dec 23, 2015, 5:20 AM

Post #25 of 28 (759 views)
Re: 94 sierra thermac Sign In

I'll try water with some food coloring, with the fan running at all times smoke might not be best,and it wouldn't be with a cigar. don't know how I'd manage that anyway. And there's no catalytic,The exhaust looks custom so I don't know if it came with one, no telling what someone has done.






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